php - GROUP_BY 中的错误，查询来自两个数据库 CODEIGNITER

Question

我有一个连接来自两个不同数据库的表的查询。它已经在显示结果，但后来我只想显示独特的结果，因为有些结果是多余的。因此，我添加了一个 GROUP BY 以仅获取唯一结果，但出现错误。

这是我的代码:

public function search_results_accommodations($location,$from_date,$to_date,$bedroom,$guests)
{
    $this->db->select('*, akzapier.bookings.id as BOOKING_ID, akzapier.properties.id as PROPERTY_ID, ci_alexandrohomes.assigned_property.ID as ASSIGNED_PROPERTY_ID, ci_alexandrohomes.listings.ID as LISTING_ID');
    $this->db->from('akzapier.bookings');
    $this->db->join('akzapier.properties', 'akzapier.properties.id=akzapier.bookings.property_id', 'inner');
    $this->db->join('ci_alexandrohomes.assigned_property', 'ci_alexandrohomes.assigned_property.property_id=akzapier.properties.id', 'inner');
    $this->db->join('ci_alexandrohomes.listings', 'ci_alexandrohomes.listings.ID=ci_alexandrohomes.assigned_property.listing_id');
    $this->db->where('akzapier.bookings.check_in !=', $from_date);
    $this->db->where('akzapier.bookings.check_out !=', $to_date);
    $this->db->where('ci_alexandrohomes.listings.city', $location);
    $this->db->where('ci_alexandrohomes.listings.bedrooms', $bedroom);
    $this->db->where('ci_alexandrohomes.listings.guests', $guests);
    $this->db->group_by('akzapier.properties.id', 'ASC')
    $query = $this->db->get();
    return $query->result();
}

页面中没有显示错误，所以我将其转换为 SQL 以查看实际情况:

SELECT * akzapier.bookings.id as BOOKING_ID, akzapier.properties.id as PROPERTY_ID, ci_alexandrohomes.assigned_property.ID as ASSIGNED_PROPERTY_ID, ci_alexandrohomes.listings.ID as LISTING_ID
FROM akzapier.bookings 
INNER JOIN akzapier.properties ON akzapier.properties.id=akzapier.bookings.property_id
INNER JOIN ci_alexandrohomes.assigned_property ON ci_alexandrohomes.assigned_property.property_id=akzapier.properties.id
INNER JOIN ci_alexandrohomes.listings ON ci_alexandrohomes.listings.ID=ci_alexandrohomes.assigned_property.listing_id
WHERE akzapier.bookings.check_in != '2019-09-21'
AND akzapier.bookings.check_out != '2019-09-30'
AND ci_alexandrohomes.listings.city = ‘1’
AND ci_alexandrohomes.listings.bedrooms = '2'
AND ci_alexandrohomes.listings.guests = '4'
GROUP BY akzapier.bookings.property_id ASC

错误提示:

1055 - Expression #1 of SELECT list is not in GROUP BY clause and contains nonaggregated column 'akzapier.bookings.id' which is not functionally dependent on columns in GROUP BY clause; this is incompatible with sql_mode=only_full_group_by

Answer 1

通常，当您使用 GROUP BY 时，您的 SELECT 语句必须包含聚合(例如 MAX(...)、COUNT(...) 等)或者列必须出现在 GROUP BY 中。您已选择所有带星号 * 的非聚合字段。在这种情况下，它提示字段 akzapier.bookings.id，它既没有聚合，也不在您的 GROUP BY 中。

如果您确实需要唯一值，请尝试使用 SELECT DISTINCT，这将从结果中删除重复的行。